Tokkai Sho 63-130953 published by the Japanese Patent Office in 1988 discloses an angular ball bearing used as a structure for supporting the input/output shafts of a toroidal continuously variable transmission.
In this toroidal type continuously variable transmission, power rollers gripped between an input disk and an output disk transmit a drive force with a speed change ratio according to their gyration angle.
According to this prior art, the input and output shafts are coaxial, and a thrust-load and radial load acting on these shafts are supported by the angular ball bearing. The angular ball bearing comprises inner and outer wheels and a multiplicity of balls gripped between grooves formed in the wheels.
In order to prevent loss of transmitted torque due to sliding of the power rollers, the contact pressure between the rollers and the disks is generally set to be high. Oil having a high viscosity at a high pressure, e.g. traction oil, is filled in a casing of the transmission.
Since a very large load acts in the thrust direction on the angular ball bearing due to a reaction force with which the input disk and output disk grip the power roller, the contact pressure in the angular ball bearing, i.e., between the balls and grooves is high, and may exceed for example 1 GigaPascal (GPa). At such a high pressure, the traction oil becomes semi-solid. It is also known that in the case of an angular ball bearing, slip may occur between the balls and the grooves due to high thrust pressure.
However, when the traction oil is semi-solid and slip occurs in the angular ball bearing, there is a large increase of energy loss, resulting in the decrease of torque transmitting efficiency of the transmission.